Cold Frame Temperatures

I'm going to keep tabs on the forecast, and how it affects the temperature recorded in my garden, and within my cold frame.

I'm using the BBC's Weather Forecast.

Date Forecast
Minimum(°C)
Cold Frame
Minimum °C)
Outside
Minimum (°C)
7th Apr 6 3.5 ?
8th 9 8.2 ?
9th 7 6.5 6
10th 5 3 0
11th 6 4 1.5
12th 6 4 2
13th 6 5 3
14th 4 3.5 1
15th 2 3 1
16th 6 3 1.5
17th 6 6 4
18th 7 6.5 4.5
19th 6
20th ? 4.5 2
21st 6 5 3.5
22nd 7 7.5 6
23rd 7 8 6
24th 7 6 3
25th 9 9.5 7.5
26th 10 9 8
27th 8

(i)